The BTG/Nexus survey put Flávio Bolsonaro ahead of President Lula 48% to 45%, or 52 to 48 in valid votes, within its margin of error. Contracts on Bolsonaro winning the Oct. 25 runoff slipped slightly after the release.
A poll that showed Brazil's presidential runoff close to even was followed by a small sell-off in contracts that price it as anything but.
The BTG/Nexus survey, released early Tuesday, gave Flávio Bolsonaro 48% and President Luiz Inácio Lula da Silva 45% in the Oct. 25 runoff, with 5% choosing neither or blank and 2% undecided. Counting only valid votes, the race was 52% to 48%. The phone poll of 2,002 voters, conducted Oct. 10 to 12, has a margin of error of 2 percentage points, which puts the gap at the edge of a statistical tie.
Rejection levels were also close. Fifty-one percent of voters said they would not vote for Lula under any circumstances, and 47% said the same of Mr. Bolsonaro. Ninety-two percent said their choice is final.
The prices
On Polymarket, the contract on Mr. Bolsonaro winning slipped from 87.45 cents at 5 a.m. Eastern to 86.65 cents at 1 p.m., touching 86.35 cents at mid-morning. On Kalshi, about 23,000 contracts traded at 87 cents in a block of seller-initiated orders at 9:31 a.m., and the price briefly printed 85 cents on a small trade before recovering to 87 cents by early afternoon.
The trading data do not show why the prices dipped after a poll favorable to Mr. Bolsonaro.
Poll versus price
The gap between the two measures is wide. A 52-48 split in valid votes, with a 2-point margin of error, describes a competitive race. A contract at 87 cents implies traders see roughly a 13% chance that Lula wins.
The two can both be right. A poll measures vote share at one moment, while the contract prices the probability of winning, which rises quickly when one candidate holds even a small, steady lead. But the price assumes the lead holds for 12 more days, through two televised debates and several more polls.
Market implications
One reading is that traders are pricing a durable lead. Mr. Bolsonaro is ahead on both total and valid votes, nearly all voters say their minds are made up, and his rejection rate is below Lula's.
A second reading is that the market is overconfident. The lead is within the margin of error, rejection rates are within four points of each other, and contracts this far from 50 cents leave little room for a late shift.
What to watch
Quaest publishes a new poll on Wednesday, and Datafolha and Palver release surveys on Thursday. Debates on Oct. 18 and Oct. 23 are the last major events before the vote, and the Brazilian real is among the assets exposed to the result.